JPS61274373A - Back plane protection sheet for solar battery - Google Patents

Abstract

PURPOSE:To increase an initial generating efficiency and avoid decline of the generating efficiency caused by penetration of moisture or the like and protect solar battery elements, internal components and the like satisfactorily by limiting the thickness of a heat adhesive resin layer. CONSTITUTION:A back plane protection sheet consists of a heat resistant and weather resistant resin film 7 which is not melted and softened at the temperature not higher than 150 deg.C and a heat adhesive resin layer 8 which is melted and softened at the temperature not higher than 150 deg.C and laminated inside the film 7. The heat resistant and weather resistant resin film 7 is provided to facilitate a heat press process as the back plane protection sheet. The thickness of the heat adhesive resin layer 8 is limited to be not less than 30mu and not more than 150mu and has Hunter whiteness of not less than 80%. The typical material of the heat adhesive layer 8 applied to glass, metal or the like is acid modified polyethylene or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laminated material used as a back protection sheet for a solar cell module.

[Constitution of conventional technology and its problems]

The basic function of a solar cell module is to efficiently guide the sun's radiant energy to the solar cell elements, and to protect the solar cell elements and internal wiring so that they can withstand harsh natural environments over a long period of time. Conventionally, solar cell modules generally have an upper transparent material (1) that serves as a structural support for the entire module, as shown in Figure 1. For example, the upper transparent material (1''N, A solar cell element (2) made of mutually wired single-crystal silicon is inserted between a back protection sheet (4) such as a painted steel plate or a fluorinated vinyl sheet sandwiched with aluminum foil, and the solar cell element (2) is made of monocrystalline silicon, etc., which is exposed to even more rapid outside air conditions. In order to prevent damage to the element due to changes in the temperature and to provide electrical insulation, the space between the upper transparent material and the lower substrate material is filled with a filler (3) such as silicone resin, and the whole is covered with a frame (3) made of aluminum, stainless steel, etc. 5).

, On the other hand, in addition to the monocrystalline silicon solar cells and polycrystalline silicon solar cell modules mentioned above, solar cells using amorphous silicon semiconductors, ■-■ group compound semiconductors, etc. as elements due to low cost orientation and mass production issues. More and more modules are being created. These solar cell modules generally have elements (2) formed by forming a thin film of element material on a substrate (1) such as a transparent plastic plate or glass plate by a method such as vapor deposition, or by printing. .

The terminals are the substrate (the edge of the layer of terminals in close contact with 11) and the conductive paste (6) on the element. These low-cost solar cells are made from high-priced materials such as conventional single-crystal silicon.
Unlike larger models, in terms of cost and simplicity, modularization is often done without using a frame made of aluminum or stainless steel, and a back protection sheet (
4) is playing an increasingly important role in protecting solar cell elements and internal wiring. There are now demands that moisture permeation from the end surfaces be as low as possible.

[Purpose of the invention]

The present invention provides a back protection sheet for a solar cell module in which elements made of amorphous silicon or n-VI group compound semiconductors are formed directly on a glass substrate by vapor deposition or printing. We provide a back protection sheet that protects components from mechanical shocks and external forces, prevents elements from breaking through, and has low moisture permeation from the edges, which improves power generation efficiency and improves power generation efficiency over time. The purpose is to provide a solar cell that does not have any degradation in energy.

[Summary of the invention]

That is, the present invention provides a heat-resistant and weather-resistant resin film that does not melt and soften at a temperature below 150° C. (the temperature at which a back protection sheet is thermally bonded to elements and internal components formed by vapor deposition or printing on a glass substrate). The present invention provides a back protection sheet for a solar cell module consisting of a laminate in which a heat-adhesive resin film that melts and softens at temperatures below 150°C is laminated on the inner surface of the solar cell module, and the thickness of the heat-adhesive resin film is is 30
μ or more and 150 μ or less, and is characterized by having a whiteness of 80% or more in Hunter whiteness according to JISP8123.

Note that acid-modified polyethylene and the like are typical examples of the heat-adhesive film of glass, metal, etc. used in the present invention.

[Detailed description of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings. Figure 3 shows the back protection sheet (4) for solar cell modules of the present invention.
1 is a cross-sectional view showing one embodiment of the present invention, which is composed of a heat-resistant/weather-resistant resin film (7) and a heat-adhesive resin layer (8) on the inner surface thereof. The heat-resistant and weather-resistant resin film (7) is
It is provided as a back protection sheet to provide heat press workability, and it does not melt or deteriorate due to the heat applied during the heat press process during the production of solar cell modules, and it is not actually used as a solar cell. A resin film is used that does not deteriorate due to sunlight, rain, etc., even under outdoor exposure conditions during storage. In particular, the conditions for heat press are usually 15
Since heat of about 0°C is applied, the resin film must not melt and soften at temperatures below 150°C. For example, perfluoroalkoxy 4tt resin, tetrafluoroethylene-hexafluoropropylene copolymer, perfluoroethylene-perfluoropropylene-perfluorovinylether terpolymer, ethylene-47fluoroethylene copolymer, In addition to fluororesin films selected from chloride-trifluoroethylene resin, polyvinylidene fluoride, and polyvinyl fluoride, polycarbonate, polymethyl methacrylate, polyacrylate, or ultraviolet absorbers (e.g., benzophare, benzo I-IJ azole, etc.) There is a kind of film selected from polyethylene terephthalate impregnated or kneaded with or a composite film of these,
These films may be ones in which a white extender pigment such as titanium oxide is kneaded, or they may have white peta printing on at least one side to increase the whiteness.

Regarding whiteness, a heat-adhesive resin layer (8) that has heat-adhesive properties with glass or metal is applied on a heat-resistant and weather-resistant resin film.
Thermal adhesive resin layer (8) of the back protection sheet (4) provided with
Light is applied from the side at an optical direction of 45 degrees and the whiteness is measured.

The measurement of whiteness is performed using a color difference meter according to JISP8123.

The inventor's experimental results revealed that the difference in whiteness of the back protection sheet (4) affects the power generation efficiency of the solar cell module. In other words, high whiteness means that
This means that the reflectance of light is high, so sunlight that passes through the upper glass substrate of the solar cell module and reaches the back protection sheet (4) without being electrified in the element is reflected on the back protection sheet (4). This seems to be because most of the light was reflected, and the reflected light again contributed to power generation in the element. According to experiments conducted by the present inventors, the value of whiteness is, for example, Cd
In a solar cell module using an element formed by a 5-CdTe system (cadmium sulfide-cadmium telluride system) printing method, when a back protection sheet with a whiteness of 80% or more is used, the power generation efficiency is 5. 5%, but for back protection sheets with a whiteness lower than that,
Power generation efficiency decreased to less than 5%. Therefore, the whiteness measured from the heat-adhesive resin layer (8) side of the back protection sheet (4) in the present invention was defined as 80% or more. As described above, the means for increasing the whiteness is not particularly limited, and may include a method of kneading a white pigment into the heat-resistant and weather-resistant resin film (7), a method of solid printing with white ink, etc. In addition, heat-resistant and weather-resistant resin film (7
) may be normally 12 .mu. or more, but in consideration of workability during module forming work, it is preferably 30 .mu. or more.

Next, the heat-adhesive resin layer laminated on the heat-resistant and weather-resistant resin film (6) will be explained. The thermoadhesive resin layer itself has adhesive properties to the glassy and metallic surfaces of the solar cell element, and is made of a resin that melts and softens at a temperature of less than 150°C, preferably 120°C or less. . Specifically, ethylene-acetic acid such as polyvinyl butyral, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-glycidyl methacrylate terpolymer, ethylene-vinyl acetate partially saponified product-organic acid graft quaternary copolymer, etc. Resins made of modified vinyl copolymers, carboxyl group-containing polyolefins such as maleic anhydride kraft polyethylene, and polyester modified resins such as ethylene terephthalate-modified alkylene ether terephthalate block copolymers are used. The thickness is 30μ or more, especially 50μ to protect internal parts such as elements formed by vapor deposition or printing.
It is desirable that it is μ or more. If it is less than that, the resin part is likely to be damaged by wiring or the like. However, considering the moisture permeability (infiltration of moisture) from the end surface of the heat-adhesive resin layer (8) of the back protection sheet, the thickness of the heat-adhesive resin layer (8) is 1
Up to about 50j. According to experiments conducted by the present inventors, when a solar cell module is made with a back protection sheet in which the thickness of the thermally adhesive resin layer (8) is 150μ or more, 65°C-9
A storage test was carried out for 1000 hours in a high temperature and humid atmosphere of 5% R and H, and the subsequent power generation efficiency was measured, and it was found that the power generation efficiency had decreased by more than 5% compared to the initial power generation efficiency. Note that when the thickness of the thermoadhesive resin layer (8) was 150 μm or less, the power generation efficiency was equivalent to the initial power generation efficiency. That is, when the thickness of the heat-adhesive resin layer (8) exceeds 150 μm, moisture permeates through the end face, deteriorating the solar cell element and reducing power generation efficiency.

Therefore, in the present invention, the thickness of the thermoadhesive resin layer (8) is defined as 30 to 150A. In addition, 65℃-95
%R1H, 1000 hours environmental test is a general evaluation standard for solar cell modules.

Furthermore, the method of laminating the heat-resistant/weather-resistant resin film (7) and the heat-adhesive resin layer (8) is not limited to a dry lamination method using an adhesive, a heat lamination method, and a heat-adhesive method. If the resin layer can be easily extruded as a resin, it may be laminated by extrusion lamination, and the lamination method is not particularly limited.

When the back protection sheet (4) of the present invention is applied to a solar cell module, the back protection sheet is applied to the solar cell element side of the glass substrate on which the solar cell element formed by vapor deposition or printing method and electrodes, etc. are further provided. The heat-adhesive resin layer (8) sides are put together, and the whole is pressed at 140° C. to 150° C. while reducing the pressure to a vacuum to fuse and integrate.

〔Example〕

(a) White ink is printed on the entire surface of a 38μ thick weather-resistant polyester film (manufactured by Toshi Co., Ltd., Q-37) kneaded with an ultraviolet absorber using a silk printing method as a base;
On this printed surface, an organic acid gellast polymer of partially saponified ethylene-vinyl acetate (manufactured by Takeda Pharmaceutical Co., Ltd., DEEMILAN F) is applied.
were formed to have 25 tones and a thickness of 100μ, 140jl, and 200μ, respectively. In addition, in order to change the whiteness of this Dumilan F formed to a thickness of 100 tones, two types were prepared with different white ink printing.

(b) The solar cell body used was one in which an n-■ group compound semiconductor (CdS-CdTe system) was formed as an element on a glass substrate by a silk printing method. The size is 30
X30Cm, power generation is 4.5W.

Each sheet obtained in (a) above was placed on the element side of the solar cell main body at 150°C under vacuum at 5 kg/L1.
They were pressed and bonded together under conditions of 0 minutes to produce a solar cell Modineal.

At this time, in the case where Dumilan F was 25μ, the element broke through the sheet.

(c) The remaining solar cell module at 85℃-95%R,
It was stored in an atmosphere of H for 1000 hours, and the power generation efficiency was compared with the initial performance. The results are shown in Table 1 along with the whiteness of each sheet.

Note that the whiteness was measured at 45 degrees in the optical direction from the Dumilan F side in accordance with JISP8123.

Table 1 As shown in the table above, it is thought that the solar cell element of Sample 3 deteriorated due to moisture infiltration from the end face of the thermal adhesive resin layer, and the whiteness of the sample was lower than that of the one-sided protective sheet of the present invention. It seems that the reflected light was not sufficiently utilized for power generation.

〔Effect of the invention〕

As described in detail above, the back protection sheet for solar cell modules of the present invention improves the initial power generation efficiency by limiting the thickness of the thermal adhesive resin layer, and the environmental test assuming outdoor exposure. Even in this case, there is no reduction in power generation efficiency due to the infiltration of moisture, and the solar cell elements, internal parts, etc. are well protected.

Also, if the whiteness of the back protection sheet is 80% or more,
It can also be expected to improve power generation efficiency.

[Brief explanation of the drawing]

1 and 2 are explanatory cross-sectional views of the solar cell module, and FIG. 3 is a cross-sectional view of the back protection sheet of the present invention. (1) - Upper transparent material (substrate) (2) - Solar cell element (3) - Filler (4) - Back protection sheet (5) - Frame (6) - Conductive paste (7) - Heat-resistant/weather-resistant resin film (8) - Heat-adhesive resin Figure 1 Figure 2 Figure 3 Large

Claims (2)

[Claims] (1) In a back protection sheet for a solar cell module in which a heat-adhesive resin layer is laminated on the inner surface of a heat-resistant/weather-resistant resin film, the thickness of the heat-adhesive resin layer is from 30 μm to 150 μm.
A back protection sheet for solar cell modules characterized by μ. (2) Back surface protection for a solar cell module according to claim 1, characterized in that the whiteness when irradiated with light at 45 degrees in the optical direction from the heat-adhesive resin layer side is 80% or more. sheet.